There has been a continuing need for couplers that release development inhibitors (so-called Development Inhibitor Releasing or "DIR" couplers). In particular, such couplers that form magenta dye upon release of the inhibitor are desirable for use in magenta dye imaging layers of silver halide photographic elements. Especially useful would be magenta dye-forming pyrazolone couplers capable or releasing azole development inhibitor groups. A number of patents have disclosed such compounds. A problem with such compounds is that their synthesis on a commercial scale has proven exceedingly difficult. Proposed synthesis routes have provided poor yields, employed carcinogenic raw materials, or have otherwise been unsuccessful.
The processes of the art suggest first forming the pyrazolone moiety and then appending the N-heterocycle. U.S. Pat. No. 4,095,984 describes a certain benzotriazole inhibitor group appended to any coupler moiety. Synthesis Example 4 at column 23 describes a method of preparing the coupler employing hexamethylphosphotriamide. This material is a carcinogen and its use is therefore undesirable. It is further described that the temperature is high (110.degree. C.), the reaction is slow (8 hrs.), and the yield is about 30%, all of which are unsatisfactory for commercial purposes. The same type of synthesis is shown in U.S. Pat. No. 4,076,533.
U.S. Pat. No. 4,241,168 shows a synthesis not involving the formation of an azolyl acetate ester in which the yield is low (about 30%). U.S. Pat. No. 4,105,656 shows a synthesis not involving the formation of an azolyl acetate ester in which the yield is about 15%. GB Patent 1,603,223 describes some of the difficulties in manufacturing such pyrazolone couplers. Generally, these methods involve attaching the desired azole group to the coupler moiety as a last step. U.S. Pat. No. 4,262,087 and EP 0 087 388 use a conventional chloroacetoacetate route rather than using an azolylacetate.
U.S. Pat. No. 5,521,318 discloses a process for making yellow rather than magenta couplers utilizing a chloro ketone rather than a chloro ester and using an isocyanate rather than an isothiocyanate as preferred in this invention.
A problem to be solved is to provide a process for making 2-azolyl-2-arylcarbamoyl acetate esters and 2-azolyl-2-arylthiocarbamoyl acetate esters and a process for using such compounds which processes are simple, safe, and provide good yields.